There are a number of different therapeutic approaches to treating respiratory diseases such as asthma and chronic obstructive pulmonary disease (COPD). For example, corticosteroids, β2-adrenergic receptor agonists, phosphodiesterase (PDE) 4 inhibitors, PDE 3 inhibitors, leukotriene receptor antagonists, epidermal growth factor receptor (egfr) kinase inhibitors, p38 kinase inhibitors, NK1 agonists and muscarinic receptor antagonists are all known for use in the treatment of respiratory diseases.
RPL554 (9,10-Dimethoxy-2-(2,4,6-trimethylphenylimino)-3-(N-carbamoyl-2-aminoethyl)-3,4,6,7-tetrahydro-2H-pyrimido[6,1-a]isoquinolin-4-one) is a dual PDE3/PDE4 inhibitor and is described in WO 00/58308. As a combined PDE3/PDE4 inhibitor, RPL554 has both anti-inflammatory and bronchodilatory activity and is useful in the treatment of respiratory disorders such as asthma and chronic obstructive pulmonary disease (COPD).
It is known that different classes of respiratory drugs may be used in combination for the treatment of respiratory diseases. However, synergistic interaction between the components of such combinations is rarely observed.